Silane-based resins that can be photochemically and/or thermally structured, single-step method for their production, parent compounds and production methods that can be used for said resins

ABSTRACT

A silane resin that can be structured photochemically and/or thermally is obtained by at least partial condensation of a mixture of a) at least one silane compound R a R 2   b SiX 4-a-b  wherein R is a group polymerizable photochemically and/or thermally via an organic group by radical or cationic polymerization; R 2  is a straight-chain, branched, or cyclic C 1 -C 12  alkyl group; X is identical or different and is a leaving group; a is 1 or 2; b is 0 or 1; a+b is not more than  2 ; and b) at least one silanediol R 1   2 Si(OH) 2  wherein R 1  is identical or different and is a straight-chain, branched, or cyclic C 1 -C 12  alkyl group or a group polymerizable photochemically and/or thermally via an organic group by radical or cationic polymerization, provided the group does not contain aryl. The silane resins have dielectric properties useful in extremely high frequency applications.

This application is a divisional application of U.S. patent applicationSer. No. 10/491,588 having a filing date of Apr. 2, 2004, the disclosureof which is incorporated in its entirety into the instant application;which application Ser. No. 10/491,588 is a national stage filing ofinternational application No. PCT/EP02/11160 having a filing date ofOct. 4, 2002 and the disclosure of which is incorporated in its entiretyinto the instant application.

BACKGROUND OF THE INVENTION

The present invention relates to silane resins that can be structured(also referred to as organically modifiable (hetero) silicic acid polycondensates or organopolysiloxanes) that are reacted when exposed toradiation (in particular, in the UV range) or reacted thermally toinorganic-organic, O—Si—O group containing hybrid polymers with improveddielectric properties as well as excellent substrate adherence and, inparticular, can be processed to structured layers. These materials aresuitable for use in high and extremely high frequency ranges (forexample, as multi-layer systems in SBU (sequential build-up) technology,in multi-layer thin-film circuits (TFC)). The invention further relatesto a method for producing such silane resins. Finally, the inventionrelates to intermediates with which the aforementioned polymers can beproduced, as well as a method for their preparation.

Polymers are used in various day-to-day applications well as in a seriesof high-tech uses (for example, information acquisition, informationprocessing, and information transfer). Compared to purely organicpolymers, organic-inorganic hybrid polymers, for example, those that arecommercially available under the trademark ORMOCER® registered to theFraunhofer Gesellschaft, exhibit in general excellent temperatureresistance and thermal shape stability, excellent adherence to aplurality of materials, and many other beneficial properties. Suchhybrid polymers are prepared in general by the so-called sol-gel processaccording to which the monomer or pre-condensed components (in general,optionally organo-modified silanes, partially in combination withadditional metal-alkoxy compounds and/or other compounds) are subjectedto hydrolysis and condensation of the appropriate groups. Afterremoving, exchanging or supplementing the solvent that is present or thesolvent that has been produced, a low viscosity to high viscosity resinor a lacquer is obtained that can be brought into a suitable form, forexample, as a coating of substrate, as a shaped body, or as a diaphragmthat, after shaping, can be dried, optionally can be cured further bypolymerization of the organic groups that are present. Thelast-mentioned organic polymerization, if desired, can be realized onlyat predetermined locations, for example, for curing by selectiveirradiation by means of actinic radiation, wherein subsequently thematerial that has not been polymerized can be removed by means ofsuitable solvents. In this way, it is possible to obtainphoto-lithographically structured three-dimensional bodies or surfaces.For example, DE 199 32 629 A1 discloses organo-modified silicic acidpolycondensates that are stable under storage conditions, can beUV-cured and can be photo-structured; the polycondensates aretransparent in the near infrared range (NIR). These resins can be used,for example, as a photoresist, as a photoresist with negative resistbehavior, or as a dielectric (generally an insulating material) formicrosystems technology (includes inter alia microelectronics,microoptics, and micromechanics).

Support materials for thin film circuits are partially ceramic materialsthat are directly developed for hybrid applications; silicon wafers; ororganic materials of the printed circuit board technology andsemiconductor technology. Their dielectric or other properties, however,would not appear to make them useful in application in connection withthe extremely high frequency range. For example, commercially availabledielectrics (for example, benzocyclobutene: BCB such as Cyclotene™4026-46 of the Dow Chemical Company; polyimide PI: Pyraline™ 2722 of theDuPont Company; or glass fiber-reinforced PTFE laminate: RT/Duorid™ 5880of the Rogers Corporation) exhibit good dielectric properties (forexample, ε_(r)<3 and tan δ=40−8·10⁻³) within the low high frequencyrange (10 kHz). Moreover, with the aforementioned glass fiber reinforcedPTFE laminate it has been shown also that attenuation values tanδ<3·10⁻³ in the lower extremely high frequency range at approximately 10GHz can be obtained. The class of polyimides that can be structured byUV and the class of the benzocyclobutenes exhibit stability at highertemperatures but are designed only for thin film applications(processable film thickness for each layer ≦25 μm) and require curingconditions that must be critically reviewed in connection with sensitivecomponents. A further disadvantage of these materials resides in thatthe adhesion strength varies greatly with the substrate properties andthat these materials partially cannot be structured by means ofconventional lithography. The high mechanical and thermal stabilityexpected from the dielectric is not ensured when using such materials.

Inorganic-organic hybrid polymers containing O—Si—O groups are alsosuitable for use in the microelectronics industry. Resins and lacquersof such materials can have properties that enable their use asdielectrics in the low high frequency range. With them, it is possibleto obtain, for example, dielectric constants of up to ε_(r)≈3 anddielectric loss of up to tan δ≈4·10⁻³ at 10 kHz. For applications inhigh and extremely high frequency range the known materials are notuseable however. For example, it was found that the UV-structured resinsdisclosed in the already mentioned DE 199 32 629 A1, which resins,because of their high transparency and good mechanical properties, wouldappear to be well suited for applications considered in the instantinvention, exhibit significantly decreased values within the extremelyhigh frequency range (in the GHz range). For example, a polymer ofdiphenyl silanediol and methacryloxy propyl trimethoxy silane in thisrange shows a loss of tan δ of 0.03. Accordingly, the application ofsuch materials as a dielectric for extremely high frequency applicationsin communications technology (RF sending and receiving modules;multichip modules, MCM) or in the automobile industry (distance radar,multilayer thin/thick film circuits, TFC) has not been found to besatisfying up to now. This is so because such applications pose extremerequirements with regard to the properties of the dielectric in themicrowave range, in particular, for frequencies between 10 and 100 GHz.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide materials whosedielectric properties within the high and extremely high frequency range(primarily between 10 and 100 GHz) are around ε_(r)<3 and tan δ<5·10⁻³and which, moreover, have at least partially thermal, mechanical, andadhesive properties that exceed those of conventional, purely organicmaterials employed in extremely high frequency applications.

It has been surprisingly found that materials which are produced byemploying a monomeric silanediol and at least one additional monomericsilane component and in which the silane component has at least oneorganically crosslinkable group that is bonded by carbon to the siliconatom, have the desired dielectric properties when the employedsilanediol has no aryl group.

Preferably, the employed silanediol is an aliphatic silanediol whoseorganic group preferably have a significant sterical requirement, forexample, isobutyl, isopropyl, or cyclohexyl.

The other monomeric silane component is a compound with two or threegroups which in the presence of hydroxy groups of the silanediol andoptionally of a catalyst for condensation function as the leaving groups(they will be often referred to in the following only as “leavinggroups” for reasons of simplification), for example, halogen; optionallysubstituted alkoxy, acyloxy, alkoxy carbonyl or NR³ with R³ equalhydrogen or lower alkyl. Alkoxy groups with particularly one up to fourcarbon atoms and lower alkyl groups of the same chain length arepreferred. In principle, the leaving groups can also be OH groups.However, this is less favorable because the inorganic condensationreaction produces water that, in turn, can cause a reversibility of thereactions so that secondary reactions can no longer be excluded (seealso infra). Moreover, the aforementioned silane component, asmentioned, has one or two organically crosslinkable groups that arestable with regard to hydrolysis and can be polymerized thermally and/orphoto-chemically, for example, in the presence of UV photo-initiators.This group/these groups is/are bonded by a carbon to the silicon atom.

The aforementioned hybrid materials can be prepared by a single-stepmethod wherein the reaction is carried out preferably in the absence ofwater. In this way, an unequivocal reaction route is forced. Secondaryreactions are suppressed. By selecting suitable condensation catalystsand defined temperature ranges and reaction times, the reaction takesplace within narrow stoichiometric limits when using the startingcomponents in suitable quantitative ratios. Surprisingly, it was foundthat the selection of the condensation catalyst can be critical in somecases. In particular, the catalyst barium hydroxide proposed in DE 19932 629 A1 is generally unsuitable. In contrast, good results can beobtained, for example, with ammonium fluorides, in particular, withtetrabutyl ammonium fluoride (in the form of the trihydrate). Because ofthe absence of water, the method reliably and reproducibly leads toproducts with the desired material properties such as viscosity,solubility, refractive index, substrate adhesion, temperatureresistance, and dielectric properties. In particular, an excellent andunexpected temperature resistance is exhibited by the materials. Thereproducibility of the course of the process is a prerequisite for thesuccess of the plurality of process steps that are required for thephoto-lithographic structure generation (application method, forexample, by spin-casting (“spin on”); pre-treatments such as pre-dryingor pre-curing; photo polymerization; intermediate treatment, forexample, postexposure bake; development; post treatment, for example,post baking), and thus for the use in the microsystems technology andfor the reliability of the component that is finally produced.

In Chemical Abstracts 1996, 127:293965 the kinetics of the photochemicalpolymerization of the reaction product of methacrylic acid(dihydroxy-methyl-silyl) methylester with dimethyl silanediol wasexamined. This reaction product and its polymerized product are notencompassed by the present invention.

The present invention moreover provides a new method with which thesilanediols to be used as a starting material can be produced. Thismethod enables the gentle preparation of silanediols in a reliable andreproducible yield; this has been a problem in the past because ofpossible secondary reactions (further reaction to polymer products).Also, previously unknown silanediols that are well suited as startingmaterials for the silane resin according to the invention can beprepared by this method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically the preparation of a silane resin accordingto the invention by employing by dicyclohexyl silanediol produced fromdicyclohexyl dichlorosilane and methacryloxy propyl trimethoxy silane.The resin can be polymerized organically, for example, by means of UVradiation (after adding UV photoinitiators) and can be optionallystructured, resulting in an inorganic-organic hybrid polymer.

FIG. 2 shows also schematically the preparation of a silane resinaccording to the invention from diisobutyl silanediol, derived fromdiisobutyl dimethoxy silane, and styryl methyl diethoxy silane as wellas the inorganic-organic hybrid polymer obtained therefrom by UVirradiation (after adding UV photoinitiators).

DESCRIPTION OF PREFERRED EMBODIMENTS

The silane resins according to the invention can be produced by means ofthe known “modified” sol-gel method. For this purpose, the silanecomponents are placed into a vessel in a suitable solvent and subjectedin a targeted fashion to a condensation reaction, preferably in thepresence of a suitable catalyst. Silane components that are suitable forcondensation are silanes of the general formula (I)R_(a)R² _(b)SiX_(4-a-b)wherein R is a group that can be polymerized by radical polymerizationor cationic polymerization in the presence of light, in particular, UVradiation, or thermally organically; wherein R² is a straight-chain,branched or cyclic, optionally substituted, C₁-C₁₂ alkyl group; whereinX is identical or different and, in the presence of an OH group andoptionally of a condensation catalyst is a leaving group; wherein a is 1or 2; wherein b is 0 or 1; and wherein a+b are not more than 2. R ispreferably selected from substituents having a significant stericalrequirement, for example, those of styryl or containing styryl,(meth)acryloxyalkyl or glycidoxyalkyl, for example, methacryloxypropylor glycidoxypropyl. Even more preferred R contains or is a styryl groupand/or a methacrylic acid group. It is particularly favorable when a is1 and b 1, wherein R is especially preferred styryl. In this embodiment,the group R² is preferably an alkyl group; most preferred in thisembodiment is R² equal methyl. However, the group R² can also bevoluminous and, for example, can be, optionally substituted, i-propyl,i-butyl, t-butyl or cyclohexyl. X is preferably selected from C₁-C₆alkoxides; methoxy or ethoxy groups are most preferred.

The silanediol is preferably a silane of the general formula (II)R¹ ₂Si(OH)₂   (II)wherein R¹ is identical or different and is a straight-chain, branched,or cyclic, optionally substituted, C₁-C₁₂ alkyl group. R¹ can be insteadalso a group that can be photochemically or thermally polymerized bymeans of an organic group, in particular, an organically polymerizablegroup that can be polymerized by cationic or radical polymerization inthe presence of UV radiation, with the proviso that it does not containan aryl group. The groups that are preferably used for R in the formula(I) are also preferred for the group R¹, with the exception of thestyryl group. However, it is preferred that the silanediol does not havean organically crosslinkable group, i.e., that R¹ is thus an alkyl groupas defined above whose optionally present substituents are selected fromthose that do not undergo polymerization, for example, halogen.

As needed, one or also several silanes of the formulas (I) and (II) canbe used. The stoichiometric ratio between the silanes of the formula (I)and those of the formula (II) is preferably exactly or approximately1:1. Preferably, the selection of the two components is such that themixture has a number of aliphatic groups that is as large as possible,i.e., both groups R¹ of the silanediol are aliphatic groups and theindex sum a+b in the compound of formula (I) is 2, wherein the group R²is then preferably methyl. Moreover, it is desirable that the aliphaticgroups in the silane of the formula (II) are at least partiallysterically demanding, for example, R¹ is isopropyl, isobutyl, orcyclohexyl.

Additionally, optionally other components (for example, for increasingthe inorganic spatial crosslinked density, the hardness, and theabrasion resistance of the resulting polycondensate) can be added, forexample, alkoxides of aluminum, boron, and germanium or transition metalalkoxides in amounts of preferably maximally 30% by weight. Otherpossible additives are conventional lacquer additives, fillers, levelingagents, and/or pigments.

The silane components are preferably used in a suitable solvent that is,if possible, free of water. Solvents can be, for example, alkoxylatedlow alkane acid esters, for example, acetic acid ester. Their estergroups are derived preferably from straight-chain or branched C₁-C₈alkyl alcohols, for example, isopropyl alcohol or isobutyl alcohol. Themixture contains preferably a suitable condensation catalyst, forexample, tetrabutyl ammonium fluoride trihydrate. Its quantity is keptso minimal that the contained H₂O does not play any significant role asa reactant in the reaction.

As needed, the mixture is carefully warmed or heated. Repeated heatingover an extended period of time to a temperature below the boiling pointof the solvent, for example, to approximately 80° C., and intermittentcooling to room temperature is beneficial. The provided reaction mediumas well as the volatile components produced by the condensation such asalcohols are removed generally at least partially, in the case ofsuitable viscosity properties also completely, for example, bydistilling on a rotary evaporator and/or optionally by means that enablelower pressures in order to complete the condensation reaction and tosuppress residual SiOH groups within the system as much as possible, orcompletely.

The products obtained in this way are generally resin-like and haveviscosities that enable further processing of the products as such.Optionally (for example, when their viscosity is too high for theproposed further processing), they can be diluted with a suitablesolvent, or an appropriate amount of solvent can be left within theresin.

In specific embodiments of the invention, the silane resins can beobtained in that a further silicic acid polycondensate, for example, inthe form of a liquid or particulate resin, or optionally also an alreadyorganically crosslinked inorganic-organic hybrid polymer, for example,in the form of solid particles, can be added to the reaction medium,before and/or during and/or after condensation of the starting materialsas described above, wherein also these materials have been obtained oroptionally have been additionally polymerized already via the containedorganic groups in accordance with the present invention. They can be thesame condensates as those to which they are admixed, for example, hybridpolymers produced therefrom. Alternatively, they can be produced fromother starting materials. In particular, when the further polycondensateor hybrid polymer differs chemically from the polymerization productthat is otherwise employed or to be produced or its potential organicpolymerization product, the admixture or embedding of these secondsilane resins or hybrid polymer components enables the combination ofdifferent properties of different resin or resin particle systems. Theproperties of the resulting polycondensates, for example, the refractiveindex, the thermal expansion coefficient or the polymerizationshrinkage, can be adapted in this way to the requirements of eachapplication.

The resins according to the invention can be structured according toknown methods thermally or photochemically, preferably in the UV range.Suitable photoinitiators in this connection are, for example, thefollowing substances obtainable from the Ciba-Geigy Company: Irgacure184, Irgacure 369, Irgacure 500, and other Irgacure compounds; as wellas the following substances obtainable from the Merck Company: Darocure1173, Darocure 1116, Darocure 1398, Darocure 1174, and Darocure 1020;and the Cyracure products of the Union-Carbide Company; moreover,benzophenone, 2-chlorothioxanthone, 2-methylthioxoanthone,2-isopropylthioxanthone, benzoine, or 4,4′-dimethoxy benzoine. Thesesubstances are conventionally employed in amounts of 0.5 to 5% by weightbased on the reaction mixture. When curing is carried out in visiblelight, the initiator can be, for example, camphorquinone. Suitable asthermal initiators are in particular organic peroxides in the form ofdiacyl peroxides, peroxy dicarbonates, alkyl peresters, perketales,ketone peroxides, and alkyl hydroperoxides. Concrete and preferredexamples for thermal initiators are dibenzoyl peroxide, t-butylperbenzoate, and azobis isobutyronitrile.

After development, three-dimensionally structured articles are obtainedthat are suitable, for example, for microsystems technologies. Theproducts exhibit very good reproducibility in regard to all materialproperties, for example, the refractive index, viscosity, temperatureresistance, processability in all process steps of UV structuring (filmthickness of 1-150 μm are preferred), as well as dielectric constants ofunder 3, preferably under 2.5. The dielectric loss tanδ in the extremelyhigh frequency range of 24 to 42 GHz or at the extremely high frequencyof 77 GHz is under 0.010, preferably under 0.004. The temperatureresistance is surprisingly high; it is, measured thermogravimetricallyaccording to Example 5, generally above 350° C., often (in particularunder nitrogen atmosphere) even above 400° C. The resins are free ofSi—OH and exhibit excellent adhesion to very different substrates, forexample, silicon, glass, metals, preferably aluminum, and other oxidicsurfaces.

Surprisingly, it was found that the silanediols used for the preparationof the silane resins can be prepared very gently and in good yields byhydrolysis of appropriate dialkyl dialkoxy silane compounds (Example 1)at a defined pH that must be very precisely maintained (in order toprevent polymerization reactions and in order to catalyze hydrolysis)and at controlled temperatures, for example, from the methoxy, ethoxy orother low alkoxy compounds. For hydrolysis, water is preferably used instoichiometric amounts or in slightly over-stoichiometric amounts. As asolvent, an alcohol such as ethanol or isopropyl alcohol, an ether suchas diethyl ether, tertiary butyl methyl ether, an ester or a ketone suchas acetone is advantageously used. The reaction is catalyticallycontrolled and governed, preferably by adding an acid such as stronglydiluted HCl for adjusting a slightly acidic pH value (in particular, inthe range of 3-4).

Moreover, it was found that the silanediols employed for producing thesilane resins can also be produced gently and in good yields from theappropriate dialkyl dihalogen silane compounds (Examples 2 and 3) byhydrolysis at controlled temperatures, for example, from fluoro, chloro,or bromo compounds. Water is preferably used in stoichiometric amountsor slightly over-stoichiometric amounts for hydrolysis. In thisconnection, for the above described reasons (danger of polycondensation)the use of trialkyl-substituted amines, preferably triethylamine, alsoin stoichiometric or slightly over-stoichiometric amounts, is mandatoryfor buffering the produced acid. As a solvent, an alcohol such asethanol or isopropyl alcohol, an ether such as diethyl ether, tertiarybutyl methyl ether, an ester, or a ketone such as acetone is usedadvantageously.

In the following, the invention will be explained in more detailed withthe aid of examples.

EXAMPLE 1

Diisobutyl Silanediol

reaction equation: (C₄H₉)₂Si(OCH₃)₂+H₂O→(C₄H₉)₂Si(OH)₂+2 HOCH₃ startingcomponents:

(1) diisobutyl dimethoxy silane 5.11 g (0.025 mol) (2) water 0.90 g(0.050 mol) (3) isopropanol 0.60 g

The components (1)-(3) are placed into a vessel at room temperature.Subsequently, approximately 3.0 g of an 0.1 n HCl solution are addeddropwise until the pH drops to 4.5. A careful pH control is requiredhere. The pH increases continuously (5-6) so that approximately anadditional amount of 0.75 g of an 0.1 n HCl solution is added until thepH remains constant at 4. The mixture is stirred at room temperature forone day until a white precipitate forms. In order to dissolve theprecipitate, approximately 14 ml diethyl ether are added; subsequently,approximately 15 ml water and 5 ml NaOH (pH 8). The two phases are thenseparated in a separating funnel; the aqueous phase is then extractedwith diethyl ether (2×10 ml) and the organic phases are combined andsubsequently washed with approximately 15 ml water. The pH check of theaqueous and organic phases provides a value of 7. The organic phase isthen dried with sodium sulfate (anhydrous). The organic phase is thenfiltered and again washed with diethyl ether.

The ether phase is then distilled on a rotary evaporator first at roomtemperature. The pressure is successively lowered within 30 minutes from600 to 14 mbar. The temperature of the water bath is increased from 20to 65° C. (at a constant 14 mbar). The distillation is interrupted atthis point because in the recipient vessel crystal formation isobserved; upon cooling and drying in air, complete crystallization isobserved. The colorless crystals are dissolved in 50 ml heptane; thenleft for 4 days at room temperature, and very fine colorless crystalneedles are formed. Finally, the crystals are filtered off and washedwith heptane.

Upon drying, very fine colorless crystal needles are formed that appearto be very voluminous (“glass wool”-like). The yield of diisobutylsilanediol is determined to be approximately 3 g which is approximately70%. The melting point is between 91-98° C.

Spectroscopic characterization:

IR (poly-(chlorotrifluoro ethylene)): v=3265 (w), 2952 (s), 2866 (s),1464 (s), 1364 (s), 1202 (s), 1125 (s), 1098 (s), 1042 (s), 969 (s), 900(s), 851 (s), 768 (s), 601 (s) cm⁻¹ ¹H-NMR (400.1 MHz, CD₃COCD₃): δ 0.64(m, 4H, —Si(CH ₂CH)₂), 0.99 (m, 12H, —Si(CH₂CH(CH ₃)₂)₂), 1.88 (m, 2H,—Si(CH₂CH)₂), 7.30 (s, 2H, —Si(OH)₂) ppm ¹³C-NMR (100.6 MHz, CD₃COCD₃):δ 24.4 (—CH), 26.2 (—CH₃), 26.5 (—CH₂) ppm ²⁹Si-NMR (79.5 MHz,CD₃COCD₃): δ approx. −8.5 ppm.

EXAMPLE 2

Dicyclohexyl Silanediol

(1) dicyclohexyl dichloro silane 50.7 g (0.19 mol) (2) tertiarybutylmethylether  260 ml (3) triethylamine 39.6 g (0.39 mol) (4) water7.60 g (0.42 mol) (5) tertiary butylmethylether  600 ml (6) acetone   60ml (7) triethylamine 1.64 g (0.02 mol) (8) pentane  560 ml

The components (3)-(6) are placed into a vessel and precooled to 4° C.,and, subsequently, the mixture of (1) and (2) also precooled to 4° C.,is slowly added in a dropwise fashion within 2.5 hours. The mixture isstirred for further 3 hours at 4° C. Since the pH value drops to 5.5,additional (7) is added, and the mixture is stirred over night at roomtemperature (RT). The precipitate is filtered off and the residue iswashed with (2). Most of the solvent (˜90%) in the filtrate is distilledoff (at 40° C.). To the residue, (8) is added and a precipitate isformed that is filtered off, washed with (8), and subsequently dried ina desiccator. The yield of the pure product was between 68, 87, and 93%(finely divided white precipitate). For these three preparations themelting point fluctuated as follows: 164.9-166.9; 164.7-168.4; and165.5-168° C.

EXAMPLE 3

Diisopropyl Silanediol

reaction equation: (C₃H₇)₂SiCl₂+H₂O→(C₃H₇)₂Si(OH)₂+2 HCl startingcomponents:

(1) diisopropyl dichloro silane 4.26 g (0.02 mol) (2) diethylether   70ml (3) triethylamine 4.76 g (0.05 mole) (4) water 0.90 g (0.05 mole) (5)diethylether   30 ml (6) acetone   70 ml

Similar to the preparation of the already known diisobutyl silanediol,the components (3-6) are placed into a vessel at 4° C., and a mixture of(1) in (2), also cooled to 4° C., is carefully added dropwise within 1.5hours and is then stirred for 1 hour at 4° C. The white precipitate iscompletely filtered off (at least two times). In the following thesolvent is distilled off from the filtrate at 40° C. (10 mbar) on arotary evaporator (40° C./10 mbar) and a very fine white precipitate isformed that is then recrystallized in heptane resulting in “glasswool”-like, colorless crystal needles that are filtered off and driedyielding 2.08 g (70%) diisopropyl silanediol. The melting point isbetween 108.5-112.6° C.

Spectroscopic characterization:

IR (KBr): v=3226 (w), 2945 (s), 2866 (s), 1464 (s), 1382 (s), 1247 (s),1031 (s), 996 (s), 877 (s), 831 (s), 730 (s), 677 (s) cm⁻¹ ¹H-NMR (400.1MHz, CDCl₃): δ 0.85-1.15 (m, 14H, —Si(CH(CH ₃)₂)₂), 2.20-2.70 (s, 2H,—Si(OH)₂) ppm ¹³C-NMR (100.6 MHz, CDCl₃): δ 12.7 (—CH), 17.0 (—CH₃) ppm²⁹Si-NMR (79.5 MHz, CDCl₃): δ −3.75 ppm.

EXAMPLE 4

Preparation of a Silane Resin According to the Invention

(1) 3-methacryloxy propyl trimethoxy silane (NT) 1.86 g (0.008 mol) (2)dicyclohexyl silanediol 1.72 g (0.008 mole) (3) tetrabutylammoniumfluoride trihydrate 4.70 mg (15.0 μmol) (4) acetic acid isobutylester 4.50 ml

The components (1)-(4) are placed into a vessel at room temperature andare heated on 6 consecutive days for 8 hours to 80° C., respectively.Inbetween, the mixture is stirred for 16 hours at room temperature.Then, the solvent is distilled off and the mixture is heated on 3consecutive days for 8 hours to 80° C. and inbetween stirred for 16hours at room temperature, respectively. Subsequently, two drops HCl (2M) are added and the mixture is again heated for 8 hours to 80° C. Afterthe mixture has become clear, the solvent is distilled off, and 3.22 g(90%) of a viscous resin remain. The refractive index n₂₀ is 1.4847.

Dielectric constant ε_(r): 2.81 and dielectric loss tanδ: 0.0045 (in theextremely high frequency range at 24 to 42 GHz, 77 GHz).

Spectroscopic characterization:

IR (NaCl): v=3500 (w), 2922 (s), 2848 (s), 1721 (s), 1638 (s), 1447 (s),1322 (s), 1297 (s), 1194 (s), 1167 (s), 1105 (s), 1020 (s), 939 (s), 911(s), 893 (s), 847 (s), 818 (s), 785 (s), 748 (s), 538 (s) cm⁻¹

COMPARATIVE EXAMPLE TO EXAMPLE 4

Example 4 was repeated but, instead of tetrabutyl ammonium fluoridetrihydrate, barium hydroxide was used as a catalyst. At the end of threedays, no reaction had been observed.

EXAMPLE 5

Preparation of a Silane Resin According to the Invention

p-vinyl phenyl methyl diethoxy silane 2.57 g (10.9 mmol) diisobutylsilanediol 2.00 g (11.4 mmol) acetic acid isobutyl ester 5.14 gtetrabutyl ammonium fluoride trihydrate 5.90 mg (18.8 μmol)

(1)-(4) were placed into a vessel and stirred for 51 hours at 80° C.(the mixture became clear after approximately 1 minute). Subsequently,the solvent was distilled off on a rotary evaporator (at 40° C., thepressure is reduced to 100 mbar within 30 minutes). The residue isstirred additionally for 19.5 hours at 80° C. and subsequently theremaining solvent is distilled off on a rotary evaporator (at 40° C.,the pressure is reduced to 6 mbar within 2 hours and distillation iscontinued for 0.5 hours at 6 mbar). The residue of 3.4 g (74%) is clearand ocher-colored and is still relatively liquid.

The refractive index n₂₀ of two samples prepared separately according tothis example was 1.5054 and 1.5075. For both samples, the dielectricconstant ε_(r) was 2.47; the dielectric loss tanδ was determined to be0.0038 and 0.0035, respectively (measured within the extremely highfrequency range at 24 to 42 GHz, 77 GHz).

The material exhibits a temperature resistance up to at least 415° C.(measured thermogravimetrically under nitrogen at a heating rate of 5°C./minute; weight loss <5%).

Spectroscopic characterization:

IR (NaCl): v=3065 (s), 2954 (s), 2897 (s), 2869 (s), 1746 (s), 1630 (s),1600 (s), 1545 (s), 1465 (s), 1391 (s), 1365 (s), 1330 (s), 1260 (s),1222 (s), 1124 (s), 1078 (s), 1017 (s), 989 (s), 953 (s), 908 (s), 832(s), 810 (s), 770 (s) cm⁻¹

EXAMPLE 6

Preparation of a Silane Resin According to the Invention

p-vinyl phenyl methyl diethoxy silane 3.47 g (14.7 mmol) diisopropylsilanediol 2.18 g (14.7 mmol) acetic acid isobutyl ester 6.83 gtetrabutyl ammonium fluoride trihydrate 7.70 mg (24.4 μmol)

(1)-(4) are placed into a vessel and stirred for 13 days at roomtemperature (the mixture became dear after 1 day). Subsequently, thesolvent is removed on a rotary evaporator (at 40° C. the pressure isreduced to 120 mbar within 15 minutes and remains at this value foranother 30 minutes). The residue is stirred additionally for 28 hours atroom temperature and is then distilled off on a rotary evaporator (at40° C. the pressure is reduced to 10 mbar within 1.25 hours and remainsat 10 mbar for 1 hour). The residue of 4.97 g (88%) is cdear andamber-colored and is still very liquid. The refractive index n₂₀ is1.5043.

Dielectric constant ε_(r): 2.59 and dielectric loss tanδ: 0.008 (in theextremely high frequency range at 24 to 42 GHz, 77 GHz).

Spectroscopic characterization

IR (NaCl): v=2945 (s), 2867 (s), 2869 (s), 1746 (s), 1630 (s), 1600 (s),1464 (s), 1390 (s), 1260 (s), 1124 (s), 1090 (s), 1025 (s), 1010 (s),909 (s), 885 (s), 832 (s), 809 (s), 759 (s), 693 (s) cm⁻¹

1. A method for preparing a silanediol of the general formula (II)R¹ ₂Si(OH)₂   (II) wherein R¹ is identical or different and is astraight-chain, branched, or cyclic, optionally substituted, C₁-C₁₂alkyl group or a group that can be polymerized photochemically and/orthermally via an organic group by radical polymerization or cationicpolymerization, the method comprising the step of: performing acontrolled hydrolysis by maintaining an acidic pH value with a lowerlimit of the acidic pH value at pH 3 of a compound of the generalformula (III)R¹ ₂Si(OR³)₂   (III) wherein R¹ has the meaning as provided for formula(II) and wherein R³ is a C₁-C₆ alkyl group; wherein the hydrolysis ofthe OR³ group is carried out with a stoichiometric amount of water or aslightly over-stoichiometric amount of water in a non-aqueous solvent.2. The method according to claim 1, wherein R³ is ethyl, n-propyl,isopropyl, or isobutyl.
 3. The method according to claim 1, wherein thepH value is approximately 3-4.
 4. The method according to claim 1,wherein the non-aqueous solvent is selected from the group consisting ofalcohol, ethers, esters, and ketones.